1. Field of the Invention
The present invention relates to a rail assembly, which has a desirable overall telescoped length of a rail assembly, stable structure, and strong strength.
2. Description of Related Art
A first conventional returnable rail device is illustrated in FIG. 10. An outer rail 70 has a T-shaped fixed unit 71 disposed on one end thereof such that the end of the outer rail 70 is enclosed. The fixed unit 71 has a slot 76 defined in a middle T-shaped stub thereof. Two sliding rails 77 are respectively disposed on two sides of the slot 76 and are parallel to the outer rail 70. The sliding rail 77 has a buckling groove 771 disposed on a front end thereof. A movable unit 72 and a buckling unit 721 disposed in the slot 76 in the T-shaped stub. The movable unit 72 has two columns 73 disposed on the two sliding rails 77 such that the movable unit 72 slides in the sliding rails 77. Two elastic units 74 are respectively mounted between the two columns 73 and the T-shaped unit 71. The buckling unit 721 is connected to the movable unit 72. The buckling unit 721 has a connecting portion defined in a top thereof. A guiding part 751 is disposed in the inner rail 75 for corresponding to the connecting portion of the buckling unit 721. When the inner rail 75 is pulled outwardly, the guiding part 751 drives the movable unit 72 moved along the sliding rail 77 to the buckling groove 771. The buckling unit 721 is fixed in the buckling groove 771 temporarily. The guiding part 751 is detached from the buckling unit 721. Conversely, when the inner rail 75 is pushed into the outer rail 70, the inner rail 75 is returned. When the guiding part 751 is contacted with the connecting portion of the buckling unit 721, the buckling unit 721 is detached from the buckling groove 771 of the sliding rail 77. The inner rail 75 is auto-returned due to an elastic force of the elastic units 74.
A second conventional returnable rail device is illustrated in FIG. 11. An outer rail 80 has a T-shaped fixed unit 81 disposed on one end thereof such that the end of the outer rail 80 is enclosed. The fixed unit 81 has a sliding rail 87 defined in a top thereof. A buckling groove 871 is defined in a front end of the sliding rail 87. A movable buckling unit 83 is mounted in the sliding rail 87. The movable buckling unit 83 has a connecting groove 831 defined therein. The movable buckling unit 83 has two buckling columns disposed on a bottom thereof for receiving in the sliding rail 87. The movable buckling unit 83 is able to slide in the sliding rail 87. An elastic unit 82 is disposed between the movable buckling unit 83 and the T-shaped fixed unit 81. A guiding part 841 is disposed on the inner rail 84 for corresponding to the connecting groove 831 of the movable buckling unit 83. When the inner rail 84 is outwardly pulled, the guiding part 841 drives the movable buckling unit 83 moved along the sliding rail 87 to the buckling groove 871. The movable buckling unit 83 is fixed in the buckling groove 871 temporarily. The guiding part 841 is detached from the movable buckling unit 83. The inner rail 84 is outwardly pulled. Conversely, the inner rail 84 is pushed into the outer rail 80. When the guiding part 841 is contacted with the connecting groove 831, the movable buckling unit 83 is detached from the buckling groove 871. The inner rail 84 is auto-returned due to an elastic force of the elastic unit 82.
A third conventional returnable rail device is illustrated in FIG. 12. An outer rail 90 has a fixed unit 91 disposed on one end thereof such that the end of the outer rail 90 is enclosed. The fixed unit 91 has two sliding rails 92 respectively defined in two sided slots of the outer rail 90. A movable buckling unit 93 is mounted in the sliding rails 92. The movable buckling unit 93 has two columns 932 formed on two sides thereof. The two columns 932 are mounted in the sliding rails 92 such that the movable buckling unit 93 is able to slide in the sliding rail 92. The sliding rail 92 has a buckling groove 971 defined in a front end thereof. The movable buckling unit 93 has an elastic unit 94 mounted between the two columns 932. The movable buckling unit 93 has a connecting portion formed on a top thereof. The inner rail 95 has a guiding part 96 defined in an inner surface thereof for corresponding to the connecting portion of the movable buckling unit 93. When the inner rail 95 is pulled outwardly, the guiding part 96 drives the movable buckling unit 93 moved along the sliding rail 92 to the buckling groove 971. The movable buckling unit 93 is fixed in the buckling groove 971 temporarily. Conversely, the inner rail 95 is pushed into the outer rail 90. When the guiding part 96 is contacted with the connecting portion of the movable buckling unit 93, the movable buckling unit 93 is detached from the buckling groove 971. The inner rail 95 is auto-returned due to an elastic force of the elastic unit 94.
The above described three conventional returnable rail devices illustrated in FIGS. 10-12, the sliding rail is disposed in the fixed unit.
A length of the sliding rail is restricted by a length of the fixed unit. The movable unit/the movable buckling unit is mounted in the sliding rail, connected with the elastic unit, and buckled with the guiding part in the inner rail. When the inner rail is pulled outwardly, the guiding part drives the movable unit/the movable buckling unit moving along the sliding rail to the buckling groove. The movable unit/the movable buckling unit is fixed in the buckling groove temporarily. The movable unit/movable buckling unit slides in the sliding rail such that a sliding stroke of the movable unit/movable buckling unit is restricted. When a three-rails telescopic device is utilized, an outer rail is mounted with the fixed unit. When a returning stroke of the movable unit/movable buckling unit is increased, a length of the middle rail is decreased. A total length and a strength of the telescopic device is decreased.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional returnable rail device.